1. Field of the Invention
The present invention relates to a photosensitive drum for use in an electrostatic copying apparatus, which is constituted by holding a cylindrical drum, having a photosensitive member or photosensitive layer provided around its outer periphery, between a pair of flanges extending axially from opposite ends of the drum.
2. Description of the Prior Art
Referring to FIG. 1, a conventional photosensitive drum is generally so arranged that, in the inner faces at opposite ends of a drum 2 having a photosensitive member 1 (thickness thereof is shown on an enlarged scale in FIG. 1 for convenience of explanation) provided around its outer peripheral surface, there are respectively formed fitting portions 7 and 8 having inner peripheral faces 7a and 8a, into which are fitted outer peripheral faces 5a and 6a of corresponding fitting portions 5 and 6 of flanges 3 and 4. In the known photosensitive drum as described above, for minimizing as far as possible the deviation or vibration of the external diameter of the drum along its circumferential direction with respect to an axis of a rotary shaft 9, it is necessary to improve the fitting accuracy between the outer peripheral faces 5a and 6a of the fitting portions 5 and 6 and the inner peripheral faces 7a and 8a of the fitting portions 7 and 8, and also the concentricity between the outer peripheral surface of the drum 2 and the inner peripheral faces 7a and 8a of the fitting portions 7 and 8. In connection with the above, there is a possibility that a deviation in the external diameter of the drum 2 tends to be increased or amplified due to a synergistic effect of deviation in the fitting tolerance between the outer peripheral faces 5a and 6a and the inner peripheral faces 7a and 8a, and also in the tolerance of the concentricity between the outer peripheral surface of the drum 2 and the inner peripheral faces 7a and 8a of the fitting portions 7 and 8. Moverover, in the prior art arrangement as described above, when the photosensitive drum is withdrawn from the apparatus housing for inspection or maintenance, it has been necessary to place the photosensitive drum perpendicularly on a plane or surface since there is a danger that the photosensitive member 1 may be damaged due to contact with the plane if it is placed thereon horizontally.
Accordingly, it is a primary object of the present invention to provide an improved photosensitive drum which is arranged to minimize the deviation in the external diameter of the drum as far as possible, and also to be free from any damage to its photosensitive member, even when the drum is placed horizontally, through substantial elimination of the technical problems as described earlier inherent in conventional photosensitive drums.